Idling control for two-cycle engines



Oct'. 27, 1953 w. c. coNovl-:R

IDLING CONTROL FOR TWO-CYCLQEJENGINES` und oct. s. i951 INVENTOR WHfQEL-W C'. CoA/07M 4 Patented Oct. 27, 1953 lIDLINGmNTRDL FCB CEE ENGINES Wonen E. onover,

rilutbwlrd, Marine :it Manufacturing Company,

Waukegan, JIL,

a. :corporation o! Delaware Application 'October 3, 195.1, 'Serial No. lM5L-'528 .BiClaimm 1 This vinvention relates 'to #an ignition control ffor regulating the iidling of an unloaded twolcycle engine.

'The rcontrol `is `des'iralcly felected by means of a Acutout switch Aresponsive to manifold pressures and *has particular -ut-ility in the Vcase of'a multiple cylinder, two-cycle engine -w'here at #least one cylinder -is permitted to Acontinue to nre without interruption. However, the invention may also be -used to cut oi completely the ignition to Aall cylinders 'until the -vacuum in the intake mani- 'fold drops Ato 'the level requisite for maintaining proper operation.

'Two-cycle vinternal 'combustion engines `are ordinarily controlled 4as 'to speed by retarding the ignition as `well as 'throttllng 'mixture intake. Such 'engines are A used in outboard motors 'having 'clutches Ifor interrupting the -drive between the engine and propeller. Such an engine, with throttled .carburetor .and ordinarily run consistentlyat low engine speeds, .with or without a load. However, if lsuch an engine is operating without load, there are 'oircumstances .under which its speed controls will not maintain it at idling speeds and all control oi- .the engine either `by throttlingthe carburetor or 'by retarding the 'ignition may .be lost. When this happens, the engine may attain .dangerously liigh and uncontrolled speeds. It has 4been found necessary to stop the `engine .by cutting ofi the ignition or by Vcompletely closing the throttle, and vthen restart. This phenomenon is notable principally ,in engines oi high power, in which internal friction represents an `increasingly minute factor.

Invariably the w'ild uncontrollable condition of the engine Vis associated with no load `and .a 'high degree of manifold vacuum. The manifold yacuum increases with a .decrease .in load `and `an increase in engine speed.

While the precise .reasons for this `phenomenon are not all clear, .itappearslikly that with a high manifold Vacuum, Ythe small `amount .of new charge pumped through itlieengine .per-.cycle is insufficient to .scavenge the `engine cylinders. Several cycles .are .requiredV .to attain .a combustible charge in .the cylinder, and when fignition finally does occur the charge is still so diluted with inert gases that .the .flame ylingers in `the cylinder to prematurely ignite the succeeding charge. This operates like an advanced spark to sharply accelerate .the engine, urtherincreasingthe'manifold'vacuum. In lany event, an objectionable and previously uncontrolled tendency to operate at 'excessive 'speeds 'when-Tree o! load 'retarded ignition lwill has been observed high powered engines of tirisftype.

Since the phenomenon Jis closely related to excessive manifold vacuum, I have found it possible to control the engine zby `means of a `vacuumoperated switch which short-circuits the ignition fto 'at least one of the engine Ycylinders until the vacuum is restored 4to normal. The shortcircuiting o'f one for more cylinders attacks the problem in two ways, frst, "by `reducing the engine power and, secondly, dby *introducing a load factor lattributable to the fact that the power of "the remaining cylinder or 'cylinders must be exerted `to operate the piston and `compress gas in `the inoperative 'cylinder or cylinders.

"While -the invention really involves Va 4very few added "parts, `the accompanying drawings show va 'typical outboard `motor assembly in Aorder `to illustrate generally'conventional parts with which the invention isindirectly concerned.

"In'the drawings:

iFig. "1 "is a View largely `in `vertical 'axial 'section through fan 4outboard motor embodying Vthe invention.

iFi'g. "2 is la View partially in horizontal section through the power head at the level ofthe 'f1y- Wheel magneto, to which has been added a diagrammatic showing ofthe control arrangement here `Jlrivolved.

"Fig '3 'is airagmentary detail view similar to Fig. 2 and 'showing `a slightly modilied arrangement.

The .conventional outboard motor as shown in Fig. l comprises ian .engine or power head A mounted at the upper end of -an upright strut B wlic'h vis 'carried by Ithe Atransom bracket C and .supports a gearhousing -D in unitary connection withthepowerhead.

uThe .power 'head comprises a crank case I in which "there is rotatably mounted a crank shaft 2 connected `bylrods `3 and '4 with I.pistons .5 and B reciprocalbl'e .in cylinders Il and 8 respectively. The cylinders have spark plugs `9 `and l0 for the ignition .of Ithe charge .delivered thereto from the crank case l according to the usual two-cycle principle.

The charge isadmitted to the crank case subllject .to .the control `of .a ,reed valve H from a carburetor [2 .through `a manifold i3. In .the manifold passage I 4 nf .the .carburetor is a throttle valve l5.

The engine crank .shaft .2 Vhas a drive shaft extension at .IB through the strut B to the lower .unit lgear case il), where the `drive shaft carries a drlvmg `gear I1 wmeshingwith driven gears It 3 and i9 which are coaxial with the propeller shaft 2B. The propeller shaft is rotatably mounted in the gear housing and extends therefrom to support the propeller 2.4. Splined to the propeller shaft is a clutch sleeve 22 adjustable from the neutral position in which it is shown in Fig. l into engagement with the jaw clutches of the driven gears is or i9 alternatively, whereby the propeller may be operated in forward or reverse.

The exhaust gases from both of the cylinders l and 8 pass downwardly through a common exhaust passage 24 to an outlet such as that shown at 25 which is normally submerged during Water operation and may conveniently be built into the rear of the anti-cavitation plate 2E.

Ignition is by the conventional flywheel magneto, wherein a magnet-carrying flywheel 2S at the upper end of crank shaft 2 is rotatable with respect to suitable cores and coils mounted on the timing plate 25, the latter being angularly adjustable for timing. Separate coils is@ and 3i and separate breaker mechanisms 32 and 33 are desirably provided ior the respective spark plugs 9 and It. y

In conventional magneto operation, each of the magneto coils comprises a primary and a second ary. The secondary is normally connected between a spark plug and ground. The primary coil has one end grounded and the other end connected to the insulatedbreaker point 33 as A best shown in Fig. 2. As the magnetic flux developed in the rotation of the flywheel magnet approaches a peak, the circuit through the coil 3i is closed by the operation of a crank shaft cam 34 upon the breaker arm 35 to allow the grounded Contact 55 carried by such arm to engage point 33 under the bias of the spring 3l to which such arm is subject. At or about the peak of the ux, the cam oscillates the breaker arm 35 in a direction to disengage point 35 from point 33, thereby breaking the circuit through coil 3i, the break inducing a sharp surge of current in the secondary to cause a spark at the plug with which the secondary is connected.

Any means of preventing such a spark from occurring will sufiice for the purposes of the present invention, provided such means may be controlled to become effective whenever the engine idling speed becomes excessive. This never happens except when the engine is free ofload,

at which time the throttle valve l5 is invariably closed or nearly closed in the manifold passage iii. Consequently, whenever the engine speed becomes excessive, there is a high vacuum in passages i3 and of the manifold.

I utilize this circumstance to effect control of ignition. l provide a vacuum duct 38 leading to the vacuum chamber 39 in a housing 40 which, for convenience, i mount at the front of the crank case. The chamber is subdivided by a nexible diaphragm 4i reeniorced by a pair of disks 42 and 43 connected through the diaphragm by a rivet and Contact button 45. yAt least the disk 43 is metallic in order to provide an electrical connection between the contact rivet or button 45 and the housing 4u through the compression spring 45 which normally maintains the diaphragm retracted in a position such that the contact 45 is out of engagement with an insulated contact 4l' constituting the head of a bolt 4S supported by dielectric grommets 49 and 50 from the inner and outer ends of a bore 5l with which housing 45 is provided. The threaded outer end of the bolt serves as a binding post to which nuts 52 and 53 are applied. The nut 52 bears against 4 the grommet 50, while the nut 53 anchors the terminal 54 of a ground wire 55 extending to the insulated breaker point 33 to which the lead 56 from coil 3l is connected in the manner above described.

The chamber 51 at the opposite side of the diaphragm 4| in housing 40 is vented to atmosphere through a duct 58.

During normal engine operation, with the throttle valve l5 at least partially open, the absolute pressure in the manifold between the carburetor and the crank case will be at least relatively high. In terms of vacuum, there will be a low vacuum in the manifold during normal operation. The pressure communicated through the vacuum line 3B to the chamber 33 of housing 4G will be inadequate to overcome the pressure of spring 46 which normally maintains the contact 45 in the retracted position in which it is shown in Fig. 2.

However, when the engine is to idle preliminary to the disengagement of clutch 22, the throttle valve will be substantially closed, leaving just suicient air for engine operation under these conditions. With the clutch disengaged, the engine has almost no load other than its internal friction and it tends to build up an excessive speed notwithstanding that the throttle valve is practically closed and the spark retarded by the usual oscillation of the timer plate 29 to sparkretarding position. Under these conditions, excessive vacuum in the manifold passages I3 and i4 will be communicated through the vacuum pipe 33 to the vacuum chamber 39 of housing 4U and the pressure differential to which the diaphragm 4l is then subject Will overcome the bias of spring 45 to engage contact 45 with contact 4i, thus shorting the coil which energizes one of the spark plugs.

Fig. 1 and Fig. 2 show means for rendering only one of the spark plugs inactive. Fig. S shows an arrangement in which each of the breaker mechanisms for the respective coils is provided with its own vacuum-operated shorting switch, branches 59 and of the vacuum line 38 being extended into the respective vacuum chambers 39 of the respective housings 4G so that both of the contacts 45 will be simultaneously engaged with contacts '41 to short both of the coils through their respective short circuiting lines 6l, thus rendering both cylinders inactive.

In either case, the cylinders will resume activity as soon as the motor slows down suiciently so that the bleeding oi air through the throttle valve will relieve the excessive vacuum. However, if all of the cylinders are simultaneously shorted out of operation, unburned mixture will be discharged from the cylinders into the exhaust passage 24 where it will explode or burn when the cylinders may resume operation. Since the combustion of any large quantity of mixture in the exhaust passage is undesirable, it is preferred to leave one cylinder in operation to dilute and scavenge these gases as rapidly as they accumulate in the exhaust passage, thereby tending to prevent any combustion at this point, or at least to cause the gases to burn harmlessly and non-explosively. Thus, in a multi-cylinder engine, it is preferred to use the arrangement diagrammatically illustrated in Fig. 2 wherein one cylinder functions normally while another is shorted out of operation.

The invention has proved successful in solving the problem of excessive speeds of two-cycle engines under the conditions recited. Even very powerful engines idle smoothly and quietly and at the requisite lreduced speed when controlled in accordance with this invention.

I claim:

1. For the control of idling speeds of substantially load-free, two-cycle engines having valvecontrolled intake manifolds, and spark plug ignition, the combination of a normally open vacuum-operated ignition-shorting switch, and a closed vacuum line operatively connected for the operation of said switch and leading thereto from said manifold for the closing of said switch when the vacuum in said manifold becomes excessive.

2. In a two-cycle internal combustion engine having an ignition system comprising a spark plug, a coil, and breaker points, said engine having a pre-compression chamber provided with an intake manifold and a valve controlling' mixture admission to said manifold; the combination of a vacuum-operated switch including a housing with an atmospheric connection and a closed connection to said manifold, said housing having a diaphragm spanning the housing between the atmospheric connection and manifold connection aforesaid, means biasing the diaphragm toward the atmospheric connection to a normally retracted position, the diaphragm being yieldable toward the vacuum connection in opposition to said biasing means when the vacuum is excessive in the manifold, a grounded contact connected with the diaphragm to be moved from its retracted position to an advanced position, an insulated contact positioned to be engaged by the grounded contact in the ade vanced position of the latter, and an electrical connection from said insulated contact to said coil for the grounding of the coil when vacuum in the manifold exceeds the value required to establish a pressure diiferential across said diaphragm for the advance of the diaphragm to engage its grounded contact with said insulated contact.

3. The device of claim 2 in which said engine comprises a plurality of cylinders having individual ignition systems, only one of which is provided with vacuum-operated short-circuiting means recited in claim 2.`

4. The device of claim 2 in which said engine comprises a multiple-cylinder engine in which the several cylinders have individual ignition systems, a plurality of said systems being respectively provided with vacuum-operated shortcircuiting switches described in claim 2.

5. The device of claim 2 in which the engine comprises a multiple-cylinder engine, the several cylinders having individual ignition systems of which less than the total number of cylinders are provided with vacuum-operated switches for short-circuiting their respective ignition systems, certain or said cylinders, including cylinders with and without said vacuumoperated short-circuiting switches, having a common exhaust discharge passage, wherein unburned mixture discharged therein as a result of the functioning of a short-circuiting switch will be diluted and scavenged with burned gases from a cylinder not controlled by such :a switch.

6. In a two-cycle engine having a manifold intake. the combination with an ignition breaker including relatively movable insulated and grounded points, of a control switch having relatively insulated and grounded contacts, a lead electrically connecting the insulated breaker point with the insulated contact of said switch, means for maintaining said switch normally open, and means for eiiecting the closing of the control switch contacts to .short circuit such breaker points when engine speed is excessive while the engine is substantially without load, said means comprising means responsive solely to relative variation in the air pressure in said manifold intake.

7. The device of claim 6 in which the control switch comprises a pressure switch having a housing, a diaphragm sub-dividing the housing into two chambers and biased toward one of them, the housing being vented whereby one of the chambers is subject to atmospheric pressure, a pressure connection to the other of the chambers, a contact button carried by the diaphragm and having an electrical ground connection, and an insulated contact carried by the housing in the path of movement of said button in opposition to said bias whereby a pressure differential overcoming said bias will engage said contacts to ground the insulated contact, said insulated contact having an electrical connection with the insulated contact of said breaker for the grounding thereof when said pressure differential is established.

8. The device of claim 7 in which the engine has a throttle-controlled mixture intake passage, the pressure connection aforesaid comprising a Ward the vented chamber.

WARREN C. CONOVER.

References Cited in the le of this patent UNITED STATES PATENTS Number 

